Depending on the hydraulic head and the associated water pressure, the remaining quantitative debris size is crucial for the wear of hydropower plant parts. The less floating matter in the drive water, the lower the wear on the pipe and turbine components. This increases the service life and profitability. Therefore, a desander is a very important part that should be always integrated in hydropower plants. Even when using a Coanda screen, a desander is a must, since it not only additional cleans the water, but it also calms the water so far that a water level can be used to control the turbine. The water level in the desander is scanned by a pressure sensor that is connected to the hydro plant control center. Based on these monitored water level data, the nozzle controller continuously optimizes generating water in the turbine. Another and usually underestimated function of the desander is to prevent an occurring pressure surge, as it can happen at any time, for example, in an emergency stop of the turbine. In such case, the desander works with its venting valves, as well as precluded by its volume, as a pressure tank. This function prevents a pipe break and reduces the pressure surge continuously.
The connecting flange is connected to the supply line from the reservoir/screen. The water flows into the metal body and hits the lamel set at an undefined flow rate. Herewith, the kinetic energy is withdrawn from the water until it approaches zero. Due to the deflection, caused by lamels, the water is braked so far that the sediments contained in the water settle in front of the flushing openings. Precisely defined impact walls prevent further transport of the sediments. At regular intervals, the flushing pipes are opened with electrically operated valves and the sediments are discharged in a regulated manner. The flushing process is so short that the turbine loses insignificant power and remains in operation (at conventional desander, it must be stopped!). The purified water leaves via chamber 2 the desander direction water pipe. In order, that no turbulence and air pockets occur in the water when entering the water pipe, the inlet cone is installed to the desander end. Air pockets reduce the performance and could lead to cavitation or even to the destruction of the water pipe.
A desander’s water level is regulated by the pressure sensor, connected to the power plant. Herewith, an optimal water level is achieved and desander’s designed performance is guaranteed. The water level is used as a constant parameter for the control of the turbine. Several pressure valves on the top of the desander ensure safe operation. For inspection and inspection work, a lockable entrance dome is installed in each desander. Best rust protection is assured with an elastic plastic paint (specially designed for underground use), covering the entire outer skin of the desander. We grant a 15-year anti-corrosion warranty on our desander and in case of signed maintenance contract, even up to 30 years. Each dispatcher is supplied with a detailed operating manual and an audit book.
- not visible in the landscape
- low maintenance costs
- easy and quick installation (normally 2 to 3 days before commissioning)
- ecologically valuable as there is no surge during rinsing
- no danger of drowning as sunk into soil
- power plant operation even at high water
- power plant operation not interrupted during the flushing process
- continuous operation results in higher efficiency of the entire system